\n 


'f'f  vers n  r  or  r c c  r Tv o ^ ^ 


j  ON  THE  RELATIONS  OF  PSYCHOLOGY  TO  OTHER 
!  SCIENCES. 

1  A  S  has  been  pointed  out  by  Herbert  Spencer,  the  growth 
of  scientific  knowledge  is  no  exception  to  the  laws  of 
evolution.  Human  sciences,  as  well  as  human  industries, 
have  undergone  a  continuous  differentiation.  To  the  mind 
of  primitive  man  the  shock  of  an  electric  discharge  and  the 
ravages  of  cerebral  disease  were  alike  manifestations  of  spirit¬ 
istic  volition.  Even  when  the  hypothesis  of  animism  had  for 
centuries  been  abandoned  by  philosophic  observers,  Lucretius 
sought  in  one  work  to  expound  the  theory  of  all  known  phe¬ 
nomena.1  But  in  recent  years  the  increase  of  knowledge  has 
brought  with  it  a  host  of  ‘ologies,’  the  specialist  in  any  one 
of  which  is  often  quite  ignorant  of  all  others. 

Nowhere  has  this  differentiation  of  the  sciences  been  shown 
more  clearly  than  in  psycho-physical  problems.  The  work  now 

(done  in  psychological  laboratories  was  begun  by  physicists 
and  physiologists.  A  physicist  made  the  first  known  measure¬ 
ment  of  the  least  noticeable  difference  of  light,2  and  an  as¬ 
tronomer  discovered  the  personal  equation.3 

When  the  laboratory  at  Leipzig  was  founded,  the  ground  was 
broken  for  the  separation  of  psychological  problems  from  those 
purely  physical  and  physiological.  Apparently  not  feeling  sure 
of  his  position,  Wundt  called  the  new  science  4  physiological 
psychology,’  and  devoted  the  first  volume,  in  which  its  exposi¬ 
tion  was  undertaken,  principally  to  physiological  questions.  But 
though  at  first  an  unwelcome  appendage  to  physiology  and 
physics,  the  new  psychology  has  now  asserted  her  right  to  recog¬ 
nition  as  a  science  separate  and  distinct  from  other  sciences,  and 
that  too  at  times  with  such  vigor  as  to  disclaim  all  relationship 
^  to  them.  Thus  Professor  Titchener  objects  to  the  use  in  psy- 

m  1  De  Rerum  Natura. 

1  2  J.  H.  Lambert,  Photometria ,  1760. 

mt  8  According  to  Wundt,  Bessel  {Physiolog.  Psychologies  4.  Aufl.,  Bd.  II,  p.  320). 


49° 


THE  PHILOSOPHICAL  REVIEW. 


[VOL.  V. 


chology  of  anthropometric  methods,1  and  Professor  Fullerton 
pleads  for  the  complete  separation  of  psychology  and  physiology.2 

It  would,  however,  be  misleading  to  consider  the  relations 
of  the  sciences  only  from  this  point  of  view.  The  progress 
of  science  is  marked  not  only  by  increasing  specialization,  but 
also  by  a  corresponding  unification. 

Physiology  is  largely  dependent  on  physics  for  the  laws  of 
arterial  pressure  and  electrotonus;  and  secretion  and  meta¬ 
bolism  are  on  their  face  complex  chemical  processes.  Optics, 
acoustics,  and  the  other  branches  of  physics  were  in  Newton’s 
time  quite  independent  of  one  another ;  they  are  now  united 
in  the  endeavor  to  explain  all  phenomena  as  transformations 
of  energy.  Chemical  reactions  can  no  longer  be  considered 
merely  transformations  of  matter,  for  the  principle  of  conser¬ 
vation  of  energy  has  been  applied  to  atomic  combinations  as 
well  as  to  molar  and  molecular  phenomena.  A  few  years  ago 
botany,  zoology,  and  physiology  had  little  in  common  ;  they 
are  now  taught  as  branches  of  biology. 

In  psychology,  perhaps,  more  than  in  any  other  science, 
this  unifying  tendency  is  manifest.  In  spite  of  the  increasing 
recognition  of  the  new  science,  psychological  literature  bristles 
with  technical  terms  of  physics  and  physiology.  If  we  survey 
the  problems  now  under  investigation,  we  shall  find  that  even 
when  the  aims  and  methods  of  psychological  research  are  sui 
generis ,  the  theoretical  interpretation  of  its  results  is  often  ini 
terms  of  the  biological  sciences.  When  psychological  meth-l 
ods  are  inadequate,  the  student  of  mind  is  often  driven  to 
biology  for  the  explanation  of  mental  phenomena.  The  study 
of  the  range  and  quality  of  sensations  leads  inevitably  to  the 
physics  and  physiology  of  nerve  stimulation  ;  fatigue  is  a 
function  of  consciousness,  but  it  is  also  a  function  of  muscle 
and  nerve  ;  space  perception  may  be  due  to  psychic  synthesis, 
but  such  synthesis  would  be  impossible  without  sensory  data, 
and  these  data  depend  upon  the  motor  mechanism  of  the  eye  ; 
association  can  no  longer  be  considered  an  ultimate  psychic 

1  Titcbener,  Philosophical  Review,  March,  1893. 

2  Fullerton,  Psychological  Review ,  January,  1896. 


No.  5.]  PSYCHOLOGY  AND  OTHER  SCIENCES. 


491 


function,  now  that  pathology  has  demonstrated  its  neural 
basis  ;  attention  is  either  another  ultimate  activity  of  mind, 
or  else  an  associative  reflex  phenomenon  ;  volition  and  move¬ 
ment  cannot  be  separated  from  the  automatism  of  all  living 
matter  ;  psychogenesis  can  now  be  studied  only  from  the  bio¬ 
logical  standpoint  ;  mental  diseases  are  no  longer  explained 
on  the  purely  psychological  theory  of  obsession  ;  the  super¬ 
stitions  of  the  illiterate  can  be  interpreted  only  by  anthropo¬ 
logical  methods  ;  and  even  those  that  adopt  the  psychological 
theory  of  suggestion  to  explain  hypnotic  phenomena,  feel  called 
upon  to  deduce  their  theory  from  physiological  principles.1 

The  laws  of  mental  phenomena  thus  seem  to  be  so  en¬ 
tangled  with  those  of  living  matter,  that  it  would  seem  impos¬ 
sible  to  say  where  one  science  ends,  and  the  other  begins. 
But  does  the  converse  relation  hold  ?  Is  physiology  similarly 
dependent  on  psychology  ?  Let  us  consider  the  history  of 
the  science.  In  its  early  development  physiology  was  as 
independent  of  physics  and  chemistry  as  psychology  was 
independent  of  physiology.  But  since  the  application  to  vital 
phenomena  of  the  principle  of  conservation  of  energy  and  the 
successful  preparation  by  synthesis  of  organic  compounds,  a 
knowledge  of  physics  and  chemistry  has  been  essential  to  the 
physiologist.  It  is  yet  to  be  seen  whether  physiology  will  be 
equally  indebted  to  mental  science  ;  but,  inasmuch  as  mental 
phenomena  accompany  human  life  as  certainly  as  do  chemico- 
physical  phenomena,  we  may  infer  that  they  also  may  be  found 
to  be  necessary  links  in  the  physiological  chain  of  causation. 
But  apart  from  the  question  of  the  ultimate  relation  of  mind 
and  body,  the  physiologist  has  been,  and  is  now,  dependent 
upon  psychology  for  one  important  method  of  investigation  ; 
for  but  a  small  part  of  what  little  is  known  of  the  functions 
of  the  brain  and  sense  organs  is  got  without  the  use  of  intro¬ 
spective  methods.2 

Thus,  in  the  present  ignorance  of  cerebral  processes,  the 
physiologist  is  by  his  use  of  psychological  methods  forced  to 

1  Cf.  Lehmann,  Die  Hypnose. 

2  Cf.  Fullerton,  op.  cit.,  for  an  analysis  of  Foster’s  Physiology  from  this  point 
of  view. 


492 


THE  PHILOSOPHICAL  REVIEW. 


[Vol.  V. 


become  also  a  psychologist;  for  the  facts  he  has  to  observe  are 
psychical  facts.  As  we  know  nothing  of  the  ultimate  relations 
of  mind  and  body,  the  only  resource  left  the  philosophical 
investigator  is  the  observation  of  the  phenomena  of  organic 
life  in  their  totality.  Since  conscious  processes  are  inseparable 
from  human  life,  the  physiologist  cannot  but  consider  these 
processes  as  parts  of  a  connected  whole.  He  has  no  right  to 
assume  that  any  one  group  of  organic  phenomena  has  no 
connection  with  other  organic  phenomena. 

I  even  see  no  good  reason  why  conscious  phenomena  should 
not  be  admitted  provisionally  as  causes  and  effects  of  bodily 
processes.  If  a  sensation  follows  the  excitation  of  a  nerve,  or 
if  a  muscular  contraction  follows  a  volition,  the  state  of  con¬ 
sciousness  may  be  assumed  to  be  part  of  the  causal  chain.  It 
matters  not  whether  there  are  other  unknown  links  in  the 
chain.  The  states  of  consciousness,  being  in  whole  or  in  part 
antecedents  or  consequents  of  physiological  processes,  must  be 
considered  in  a  comprehensive  view  of  such  phenomena.  It 
may  be  argued  that  the  concept  of  cause  and  effect  cannot  be 
applied  in  this  way.  But  since  the  time  of  Hume,  science  has 
had  no  right  to  speak  of  cause  and  effect  with  ontological 
implications.  To  deny  to  the  physiologist  the  right  to  intro¬ 
duce  sensations  and  volitions  into  his  causal  series,  would  be  to 
deny  to  the  psychologist  the  right  to  assume  material  processes 
as  causes  of  sensation  ;  yet  this  he  is  obliged  to  do,  since  we 
know  nothing  of  a  mental  counterpart  of  the  stimulus.  The 
mental  counterpart  may  exist,  but  experience  gives  us  no  clue 
of  its  existence.  Consequently  science,  being  the  systematiza¬ 
tion  of  experience,  must  neglect  it  until  there  is  other  than 
a  metaphysical  reason  for  admitting  it  in  the  causal  series. 
Even  the  advocates  of  parallelism  assume  the  physical  causa¬ 
tion  of  sensation  implicitly,  if  not  explicitly.  Fechner  holds 
that  all  matter  has  a  psychical  substratum,  but  speaks  of  the 
“  bodily  causes  of  sensations.”1  Wundt,2  Bain,3  and  others  use 

1  Fechner,  Elemente  der  Psycho-Physik,  2.  Aufl.,  Bd.  I,  p.  18. 

2  Wundt,  op.  cit.y  vol.  I,  p.  334. 

3  Bain,  The  Senses  and  the  Intellect ,  4th  ed.,  p.  101. 


No.  5.]  PSYCHOLOGY  AND  OTHER  SCIENCES. 


493 


similar  expressions.  Klilpe  distinguishes  between  the  cause  of 
a  physiological  process  and  the  condition  of  a  psychical  process, 
but  admits  that  the  physiological  concept  of  cause  includes  the 
psychological  concept  of  condition.1  Hoffding,  it  is  true,  criti¬ 
cises  the  doctrine  of  physical  causation  of  psychic  states,  but 
fails  to  tell  us  what  mental  processes  take  the  place  of  the  physi¬ 
cal  stimulus.2  They  are,  therefore,  an  unknown  hypothetical 
factor.  But  that  is  to  give  them  up  for  purposes  of  scientific 
explanation. 

I  have  spoken  especially  of  physiology,  but  we  may  easily 
extend  our  conclusions  to  the  other  biological  sciences.  Physi¬ 
ology,  the  science  of  function,  and  morphology,  the  science  of 
structure,  are  but  parts  of  a  connected  whole.  The  structures 
of  plants  and  animals  have  been  determined  by  evolution,  and 
the  process  of  evolution  is  a  physiological  process.  It  may 
seem  absurd  to  conclude  that  psychology  and  anatomy  overlap, 
but  the  Lamarckian  theory  assumes  consciousness  as  a  determin¬ 
ing  cause.  As  mental  phenomena  undoubtedly  occur  in  the  lower 
animals  and  are  clearly  related  to  those  of  man,  the  zoologist 
cannot  avoid  trespassing  on  psychological  ground.  Even  bot¬ 
any  cannot  be  wholly  separated  from  mental  science,  for  who 
can  draw  the  line  between  plant  and  animal  ?  Protoplasm  was 
discovered  in  vegetable  cells,  and  botanists  are  acquainted  with 
many  cases  of  instinct  in  plants. 

That  the  methods  of  psychology  are  often  those  of  anthro¬ 
pology,  and  conversely,  is  well  known.  If  the  psychologist 
would  know  the  phenomena  of  mind,  he  cannot  content  himself 
with  observing  simply  those  of  his  own  individual  mind.  That 
great  errors  and  misunderstandings  may  arise  from  the  failure 
to  use  the  anthropological  method  is  known  to  all  who  are 
acquainted  with  the  fact  of  individual  differences  in  mental 
imagery.  Yet  the  first  exact  examination  of  this  fact  was 
made  by  an  anthropologist.3  It  has  even  been  claimed  that 
great  systems  of  epistemology  owe  their  character  to  the'se 
individual  peculiarities.4  Anthropometric  methods  are  not 

1  Kiilpe,  Psychologie,  p.  81. 

2  Hoffding,  Outlines  of  Psychology ,  English  translation,  p.  65. 

3  Galton.  4  Fraser,  American  Journal  of  Psychology ,  IV,  p.  2. 


494 


THE  PHILOSOPHICAL  REVIEW. 


[VOL.  V. 


always  as  exact  as  those  of  a  psychological  laboratory;  but 
these  methods  are  the  only  ones  by  which  a  vast  range  of 
psychological  problems  may  be  investigated.  One  crying  need 
of  the  psychology  of  to-day  is  a  more  definite  knowledge  of 
individual  constants  and  their  relations. 

Even  in  the  present  embryonic  stage  of  the  development  of 
psychology,  it  has  many  points  of  contact  with  the  inorganic 
sciences.  In  his  study  of  sensation  the  psychologist  has  to  call 
upon  the  physicist,  for  the  relations  of  stimulus  and  sensation 
can  be  understood  only  when  we  know  what  the  stimulus  is. 
It  is  to  physical  science  that  we  owe  the  demonstration  to  a 
high  degree  of  probability  of  that  stupendous  truth  that  sensa¬ 
tions  and  their  stimuli  are  qualitatively  different,  and  that  there 
exists  a  whole  series  of  physical  phenomena  that  have  no  coun¬ 
terpart  in  consciousness.1 

That  the  physicist  is  in  his  turn  forced  to  become  psychol¬ 
ogist  is  shown  by  his  discussion  of  color  theories,  after  images, 
contrast,  and  space  perception.2  Though  starting  with  the 
assumption  of  common-sense  realism,  the  physicist  is  forced  to 
conclude  that  the  assumed  correspondence  of  sensation  to  stim¬ 
ulus  is  illusory.  As  his  aim  is  knowledge  of  objective  phenom¬ 
ena,  he  cannot  but  consider  the  relation  of  such  phenomena  to 
his  perceptions.  The  investigation  of  such  relations  is  a  physi¬ 
cal  as  well  as  a  psychological  problem.  The  physicist  studies 
the  effects  of  certain  physical  phenomena,  whereas  the  psychol¬ 
ogist  has  for  his  problem  the  physical  causes  of  these  psychic 
effects.  Thus,  psychology  and  physics  unite  in  psycho-physics. 

The  debt  of  physics  to  mental  science  may  even  be  greater. 
The  more  physical  science  has  reduced  objective  phenomena  to 
transformations  of  matter  and  energy,  the  greater  the  difficulties 
in  the  mechanical  interpretation  of  nature.3  All  such  phenom¬ 
ena  were  once  ascribed  to  matter  and  its  properties,  but  now 
we  are  told  that  energy  is  an  objective  reality,  and,  like  matter, 
indestructible.  Energy  is  transmitted  through  the  ether,  a 

1  I  refer,  of  course,  to  different  forms  of  ether  waves,  actinic  and  electromagnetic. 
The  Rontgen  rays  might  here  be  included. 

2  Cf.  Ganot’s  Physics ,  pp.  605  et  seq Barker’s  Physics ,  pp.  472-6. 

3  Cf.  Stallo,  The  Concepts  and  Theories  of  Modern  Physics ,  1885. 


No.  5.]  PSYCHOLOGY  AND  OTHER  SCIENCES. 


495 


second  immaterial  reality.  As  electricity  is  not  energy,  but  is 
indestructible,  it  is  considered  a  third  immaterial  reality.1 
Matter  is  reduced  to  atoms,  but  these  atoms  are  such  stumbling- 
blocks  that  some  would  deny  their  existence  altogether,2  and 
others  consider  them  to  be  vortex  rings  of  ether.3  But  this 
ether,  on  which  science  lays  so  heavy  a  burden,  has  properties 
that  seem  to  be  contradictory,  and  is  therefore,  it  may  be 
argued,  inconceivable.  But  if  the  objective  universe  should 
prove  unintelligible  on  the  mechanical  theory,  it  is  not  improb¬ 
able  that  physical  science  may  have  to  abandon  its  time-honored 
realism  and  assume  mind  as  the  final  reality.  That  such  a  sup¬ 
position  has  some  basis  of  fact  is  shown  by  the  attitude  of  such 
men  as  Balfour  Stewart,4  Tait,4  and  Lodge.5  According  to  the 
reports  of  the  Society  for  Psychical  Research,  we  may  have  to 
admit  the  existence  of  phenomena  subject  to  laws  apparently 
contradictory  of  the  axioms  of  mechanics,  and  determined  by 
conscious  processes.6 

We  have  seen  that  psychology  and  her  sister  sciences  are 
often  greatly  indebted  to  one  another  for  results  as  well  as  for 
methods.  But  is  this  integration  of  the  sciences  limited  to  an 
assimilation  of  methods  and  results  ?  At  first  sight  it  would 
seem  that  the  differentiation  of  problems  has  increased  in  pro¬ 
portion  to  this  assimilation  of  methods  and  results.  In  physics, 
for  example,  the  problems  seem  quite  distinct  from  those  of 
other  sciences,  since  the  physicist,  as  physicist,  studies  only 
transformations  of  energy.  But  if  mental  processes  should  be 
found  to  be  conditions  of  physical  phenomena,  the  explanation 
of  such  phenomena  would  be  psychological  as  well  as  physical. 

In  biological  science  we  find  many  problems  that  are  identical 
with  problems  of  psychology.  The  nature  and  origin  of  instinct, 
mental  evolution,  and  heredity  are  obviously  psychological 

1  This  appears  to  be  the  most  recent  view.  Cf.  Barker,  Physics ,  p.  538. 

2  Ostwald,  quoted  by  Remsen,  Science ,  III,  p.  59. 

3  Sir  William  Thomson.  See  Clerk  Maxwell,  Article  “  Atom,”  Encycl.  Brit. 

4  Stewart  and  Tait,  The  Unseen  Universe ,  London,  1895. 

5  See  Lodge  and  Richet  in  Journal  of  the  Society  for  Psychical  Research ,  March 
and  April,  1895. 

6  Cf.  Myers,  “  The  Experiences  of  W.  Stanton  Moses,”  Proceedings  of  the 
S.  P.  R.,  pt.  XXV,  vol.  IX,  and  pt.  XXVII,  vol.  XI. 


496 


THE  PHILOSOPHICAL  REVIEW. 


[Vol.  V. 


problems.  They  are,  however,  but  parts  of  a  larger  whole,  but 
special  cases  of  more  general  problems  that  belong  to  biology. 
Again,  the  relations  of  mind  and  body  are  problems  of  psychol¬ 
ogy,  but  they  are  also  problems  of  physiology  and  pathology. 
This  is  evident  if  the  conclusions  be  admitted  as  to  the  right 
of  the  physiologist  to  consider  conscious  processes  as  causally 
related  to  other  activities  of  living  matter.  That  the  problems 
of  psychology  and  pathology  are  sometimes  identical,  is  known 
to  all  who  are  interested  in  what  is  called  ‘abnormal  psychology,’ 
but  which  is  after  all  but  a  branch  of  pathology.  The  mental 
phenomena  of  disease  and  degeneration  are  but  parts  of  the 
psychic  totality,  which  it  is  the  business  of  psychology  as  the 
science  of  mind  to  systematize  and  explain.  Moreover,  what  is 
termed  the  ‘  normal  mind  ’  is  but  an  ideal  of  popular  psychology. 
The  weaknesses  and  eccentricities  of  the  normal  man  are  quali¬ 
tatively  akin  to  the  morbid  feelings  and  impulses  of  mania,  and 
the  delusions  of  paranoia.  Alienists  cannot  draw  the  line 
between  sanity  and  insanity ;  much  less  can  psychologists  draw 
the  line  between  the  normal  and  the  abnormal.  But  if  we  can¬ 
not  distinguish  between  the  normal  and  the  abnormal,  we  cer¬ 
tainly  cannot  differentiate  the  problems  of  ‘  normal  ’  and  ‘  ab¬ 
normal’  psychology. 

That  the  problems  of  anthropology  and  those  of  psychology 
are  often  the  same,  may  also  be  shown.  Many  of  the  most 
common  mental  phenomena,  from  the  feelings  and  beliefs  of 
civilized  man  to  the  play  activities  of  the  civilized  child,  can  be 
interpreted  only  as  survivals  from  prehistoric  ages.  The  expla¬ 
nation  of  such  or  any  other  mental  phenomena  is  of  course  a 
problem  of  psychology  ;  but  it  is  also  a  problem  of  anthropol¬ 
ogy,  since  that  science  has  to  do  with  all  activities  of  man  as  a 
member  of  the  human  race.  Language  and  religion,  social 
customs  and  ethical  ideals,  —  all  had  their  being  only  by  virtue 
of  psychological  laws.  Their  explanation  is  therefore  a  psy¬ 
chological  problem.  That  this  problem  also  comes  within  the 
province  of  anthropology  is  shown  by  the  space  given  to  it  in 
treatises  on  the  science.  In  fact,  comparative  psychology  might 
well  be  called  ‘  psychological  anthropology.’ 


i'i?ivri5f;rTv  or  ff.f.rr:off? 

-  -v  ;  .  ■  ■  .  ,  vr:fi  F  t!  r, 

No.  5.]  PSYCHOLOGY  AND  OTHER  SCIENCES.  497 

I  have  now  discussed  the  relations  of  psychology  and  other 
sciences  from  the  historical  or  a  posteriori  point  of  view.  We 
have  found  that  their  problems  as  well  as  their  methods  are 
often  the  same.  We  turn  now  to  a  brief  a  priori  examination 
of  the  question.  As  the  relations  of  mental  and  physical  phe¬ 
nomena  are  included  in  those  of  mind  and  body,  I  shall  only 
discuss  the  theories  of  these  relations.  But  first  I  shall  endeavor 
to  show  that  these  relations  must  be  considered  in  all  branches 
of  theoretical  psychology. 

The  purpose  of  psychological  investigation  may  be  considered 
to  be  the  knowledge,  first,  of  the  qualities  or  attributes  of 
mental  phenomena  ;  secondly,  of  the  relations  of  such  phenom¬ 
ena  to  one  another  ;  and  thirdly,  of  their  relations  to  conditions 
which  are  apparently  not  mental.  The  method  of  investigating 
the  first  of  these  groups  of  problems  is  primarily  introspection. 

Such  knowledge  may  be  quite  independent  of  the  objective 
world.  But  knowledge  of  individual  facts,  uncoordinated  and 
unrelated,  is  not  science.  Only  by  understanding  the  relations 
of  phenomena  can  we  make  those  predictions  of  phenomena 
which  should  form  the  ideal  aim  of  science.  The  investigation 
of  such  relations  leads,  it  may  be  shown,  to  the  relations  of 
mind  and  body.  For,  when  the  psychologist  fails  to  find  in  any 
purely  mental  law  the  explanation  of  any  phenomenon,  he  is 
justified  in  looking  for  an  explanation  in  the  properties  of  living 
matter.  The  other  relations  of  mental  phenomena  are  either  to 
the  body  or  to  the  environment.  The  relations  to  the  environ¬ 
ment  cannot  be  interpreted  apart  from  bodily  processes.  Thus 
psycho-physics  leads  to  psycho-physiology.  In  all  branches, 
therefore,  of  theoretical  psychology  we  may  be  confronted  by 
the  problems  of  mind  and  body. 

According  to  the  theory  of  parallelism,  as  generally  under¬ 
stood,  mental  phenomena  form  an  independent  series  superim¬ 
posed  upon  a  purely  mechanical  series.  Even  on  the  assumption 
that  the  activities  of  the  body  may  be  explained  on  mechanical 
principles,  it  is  doubtful  if  psychology  and  other  sciences  could 
remain  independent.  If  there  be  complete  parallelism,  the 
relations  of  the  series  would  require  investigation.  But  who, 


498  THE  PHILOSOPHICAL  REVIEW.  [Vol.  V. 

if  not  the  psychologist,  should  investigate  these  relations  ?  As 
science  is  but  classified  knowledge,  the  knowledge  of  these 
relations  must  come  under  the  scope  of  some  science.  No  one, 
I  think,  would  hesitate  to  call  Fechner’s  law  a  psychological 
law,  or  deny  that  it  has  a  place  in  a  text-book  of  mental 
science.  Yet,  as  formulated  by  Fechner,  the  law  gives  the 
relation  of  these  very  physical  and  psychical  series.  Then,  too, 
if  there  be  complete  parallelism,  this  parallelism  must  extend 
into  the  inorganic  world.  If  so,  it  is  probable  that  the  two  series 
are,  as  Spinoza  believed,  but  modes  of  one  and  the  same  reality. 
In  fact,  on  the  theory  of  parallelism  it  is  difficult  to  hold  to  any 
dualistic  ontology.  If  the  ultimate  reality  is  mind,  it  is  quite 
possible  that  the  physicist  will  some  day  look  to  psychology  for 
the  solution  of  problems  that  his  science  fails  to  give.  For 
physical  and  biological  science  would  then  be,  theoretically  at 
least,  branches  of  psychology.  If,  on  the  other  hand,  the  final 
reality  be  matter,  or  other  non-mental  substance,  it  is  clear  that 
psychological  laws  are  not  ultimate,  but  would  have  to  be 
deduced  from  physical  laws.  In  that  case,  psychology  and  all 
the  biological  sciences  would  be  subordinated  to  physics  and 
chemistry.  The  differentiation  of  the  sciences  would  be  a 
differentiation  for  convenience,  not  a  logical  necessity. 

It  is  generally  assumed  in  speaking  of  parallelism  that  all 
physiological  processes  are  mechanical,  but  of  this  we  have  no 
proof.  The  most  recent  biological  theories  do  not  favor  a 
mechanical  interpretation  of  life.  Even  if  consciousness  be 
epiphenomenal,  it  is  quite  possible  that  the  complete  explana¬ 
tion  of  vital  phenomena  will  include  other  than  mechanical 
causes.  We  may  therefore  assume,  as  one  form  of  the  autom¬ 
aton  theory,  that  parallel  series  of  mental  and  material  phe¬ 
nomena  occur  only  in  organic  matter.  Such  parallelism  may 
hold  for  all  activities  of  organic  matter,  or  only  for  certain  ones 
of  these  activities.  If  the  parallelism  hold  for  all  terms  of  the 
two  series,  the  conditions  would  be  the  same  as  those  just  dis¬ 
cussed  ;  the  relations  of  the  series  would  require  investigation 
and  these  relations  would  be  both  psychological  and  biological. 
Hence  psychology  and  biology  would  have  the  same  problems. 


No.  5.]  PSYCHOLOGY  AND  OTHER  SCIENCES. 


499 


If  the  parallelism  be  incomplete,  the  psychologist  and  physiol¬ 
ogist  will  seek  to  know  at  what  point  the  mental  series  begins 
and  at  what  point  it  ends.  Such  knowledge  would,  however, 
only  open  up  the  question  why  the  mental  series  began  or 
ended  at  one  point  rather  than  at  another,  —  a  question  both 
physiological  and  psychological. 

On  the  Cartesian  theory  we  may  assume  matter  and  con¬ 
sciousness  to  be  causally  related,  or  matter  and  mind,  conscious 
and  unconscious.  In  either  case  psychology  and  the  biological 
sciences  would  overlap.  We  may  even  admit  that  the  field 
could  be  divided  up  so  that  the  biologist  and  the  psychologist 
should  each  investigate  his  own  series,  the  material  or  the 
mental.  But  what  of  the  point  where  they  meet  ?  The  inves¬ 
tigation  of  this  borderland  would  be  physical,  biological,  and 
psychological.  But  there  may  be  in  organic  phenomena  no 
independent  mechanical  series  ;  all  cellular  activity  may  be 
intelligible  only  from  the  subjective  standpoint.  In  this  case 
the  provinces  of  psychology  and  biology  would  be  logically 
undistinguishable. 

From  this  examination  of  the  hypothetical  relations  of  mind 
and  body  we  conclude,  then,  that  we  cannot,  by  assuming  any  one 
of  these  hypotheses,  define  the  province  of  psychology  as  distinct 
from  those  of  other  sciences.  To  attempt  any  arbitrary  division 
of  the  ground  that  is  properly  psychological  and  that  which  is 
not,  would  from  this  point  of  view  be  absurd.  Obviously,  just 
how  far  the  domain  of  psychology  extends  into  that  of  biology 
and  other  sciences,  depends  upon  the  unknown  relations  of 
mental  and  other  processes. 

The  conclusions  to  which  we  are  led  are  largely  negative. 
They  may,  however,  be  put  into  positive  form  :  the  problems 
of  psychology  and  other  sciences  may  coincide  ;  the  unity  of 
all  science  is  not  simply  a  unity  of  methods  and  results.  The 
extent  of  this  unity  cannot,  however,  be  determined  except  by 
experience.  A  priori  reasoning  leads  to  different  results, 
according  as  we  make  different  ontological  assumptions. 

But,  it  may  be  said,  are  not  these  conclusions  at  variance 
with  our  generalization  as  to  the  progressive  differentiation  of 


500 


THE  PHILOSOPHICAL  REVIEW. 


[Vol.  V. 


science  ?  This  differentiation  will  continue  if  Spencer’s  formula 
of  evolution  is  even  an  approximation  to  the  truth.  But  the 
differentiation  will,  I  hold,  be  a  differentiation  with  reference 
to  particular  objects  of  cognition,  rather  than  to  the  subjective 
classification  of  our  cognitions,  or  to  the  methods  which  we 
employ.  We  will,  perhaps,  have  a  science  of  color  rather  than 
three  or  four  sciences  that  treat  of  the  subject  from  different 
points  of  view.  The  practical  advantage,  even  now,  of  thus 
examining  a  phenomenon  from  every  point  of  view  is  shown  by 
the  remarkable  discoveries  of  Helmholtz  in  sciences  before 
considered  quite  independent.1  Had  Helmholtz  not  been  a 
great  physicist  he  would  not  have  been  the  physiologist  and 
psychologist  that  he  was  ;  nor,  had  he  avoided  problems 
other  than  physical,  would  he  have  solved  the  mystery  of 
timbre. 

It  may  be  claimed  that  the  common  ground  of  psychology 
and  other  sciences  is  in  many  cases  pure  philosophy  ;  that 
the  relation  of  mind  and  matter,  for  example,  is  a  problem  for 
philosophy,  not  for  science.  But  no  one  doubts  that  we  have 
some  scientific  knowledge  of  the  relations  of  mind  and  matter. 
Just  how  far  such  problems  may  be  solved  we  cannot  say. 

Then  it  is  open  to  question  whether  the  sharp  Kantian 
distinction  between  science  and  philosophy  will  be  sustained. 
Even  now,  with  all  his  dislike  of  ‘guesswork,’  the  man  of 
science  cannot  steer  clear  of  metaphysical  rocks.  Thus  physics, 
the  queen  of  sciences,  has  for  its  foundation-stone  a  highly 
metaphysical  principle.  The  speculations  of  modern  mathema¬ 
ticians  on  the  fourth  dimension  are  essentially  metaphysical. 
In  biology  the  origin  of  terrestrial  life  and  the  evolution  of 
man  are  wrapped  in  such  mystery  that  some  would  invoke 
transcendental  causes.2  In  mental  science  space  perception, 
association,  and  other  processes  are  quite  entangled  with  the 
problems  of  epistemology  ;  and,  if  Myers 3  is  right  and  retro- 


1  An  interesting  exposition  of  Helmholtz’  services  to  psychology  is  given  by 
Stumpf,  Archiv  f  Geschichte  d.  Phil.,  Bd.  VIII,  Heft  3,  1895. 

2  Wallace,  for  example. 

3  Myers,  Proceedings  of  the  S.  P.  R.,  pt.  XXIX,  vol.  XI. 


No.  5.]  PSYCHOLOGY  AND  OTHER  SCIENCES. 


501 


cognition  and  precognition  are  facts,  science  may  yet  have  to 
consider  the  hypothesis  of  an  immanent  world-soul.  Thus 
objective  science  has  to  face  the  problem  of  ontology,  and  sub¬ 
jective  science  also  that  of  epistemology.  And  this  is  but  what 
we  might  expect.  After  all,  the  scientist  and  philosopher  have 
the  ‘same  object  ;  both  seek  truth,  though  they  seek  it  by 
different  paths. 


Harold  Griffing. 


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